The present disclosure relates to a bonding pad for thermocompression bonding, to a component and also to a process for producing a bonding pad.
In thermocompression bonding, two metallic faces can be permanently connected to one another. To this end, the faces are pressed onto one another with a high pressure and at an elevated temperature until restructuring of the crystal grains which leads to a bond between the faces is effected at the contact interface of the metals.
By way of example, US 2010 283 138 A1 describes a process in which nickel is used as the bonding metal for a MEMS component. In this case, the bond is effected directly by way of the nickel layers. Here, a nickel-based material is connected to a further nickel-based material or an aluminum-based material at a connection point.
A plurality of metals can be used for wafer bonding by means of the thermocompression bonding process. These metals are described in a number of publications (e.g. “Investigations of thermocompression bonding with thin metal layers”, Proceedings of Transducers 11). In this respect, Al, Cu and Au are common. In the case of Al and Cu, there is the risk of oxide formation on the surface before the bonding, which can have an adverse effect on the adhesion to the bonding interface. Au as a bonding metal here has advantages, but it is relatively expensive to produce in thick layers.
U.S. Pat. No. 7,737,560 describes a process for forming a wire bonding connection with the aid of ultrasound, said process using a layered bonding pad metal system with an Ni-containing layer and a passivation layer, e.g. of Pd and Au, located thereabove.
Against this background, the present disclosure proposes a bonding pad for thermocompression bonding, a component and also a process for producing a bonding pad according to the description below. Advantageous configurations become apparent from the description which follows.